An investigator wants to estimate caffeine consumption in high school students.

Question

An investigator wants to estimate caffeine consumption in high school students.
A)- How many students would be required to ensure that a 95% confidence interval estimate for the mean caffeine intake (measured in mg) is within 15 units of the true mean? Assume that the standard deviation in caffeine intake is 68mg

B)-How many students would be required to estimate the proportion of students who consume coffee? Suppose we want the estimate to be within 5% of the true proportion with 95% confidence. please show work.

Explanation / Answer

a. Given a=0.05, |Z(0.025)|=1.96 (check standard normal table) So n=(Z*s/E)^2 =(1.96*68/15)^2 = 78.94915 Take n=79

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